Apparatus for extruding and straining compounds



April 155 1952 G. E. Guss APPARATUS FOR EXTRUDING AND STRAININGCOMPOUNDS `Fils-2d May 2l, 1949 20 I 2 Amsx vl/5N To@ G. E GL /55 .9VATTORNEY Patented Apr. 15, 1952 APPARATUS FR EXTRUDING AND STRAININGCOMPOUNDS George E. Gliss, Baltimore,` Md., assignor to Western ElectricCompany,1ncorporated, New York, ;V p N. Y., a corporation of New YorkyApplication May 21, 1949, SerialNo. 94,646

This invention relates toapparatus for extruding and straining organic`compounds, and more particularly to apparatus for straining elastomercompounds as they are extruded into iinishedarticle form.

In `the manufacture of insulated conductors, elastomer compounds oftenare `extruded into coveringsaround. conductive cores, and are sometimesstrained as they are so extruded. Strainers known hitherto have causedcaking of the compounds passing therethrough, havebeenxdifi'lcult toclean,i and have seriously impeded flow of compounds therepast.

An object of the inventionis to provide new 'and improved apparatus forextruding and straining organic compounds.

A further object of the invention is to provide new and improvedapparatus for straining elastomer compounds as they are extruded intoiinished-article form.

Another object of the invention is to provide apparatus for strainingvulcanizable compounds without causing caking of the compounds andwithout seriously impeding flow of the compounds, and which may becleaned easily.

An apparatus illustrating certain features of the invention may includean extrusion cylinder having a bore therein, a stock screw rotatable inthe bore for forcing plastic material through the bore and an extrusionhead having an opening therein in communcation with the bore to form apassage therewith. The apparatus is provided with means for strainingmaterial which comprises a screen positioned in the passage, and

a spider-like backing plate positioned in the passage forsupporting thescreen.

A complete understanding of the invention may be obtained from thefollowing detailed description of an apparatus forming a specicembodiment thereof, when read in conjunction with the appended drawing,in which:

Fig. 1 is a fragmentary, horizontal section of an apparatus forming oneembodiment of the invention;

Fig. 2 is an elevation of a portion of the apparatus shown in Fig. l,and

Fig. 3 is an enlarged section taken along line 3-3 of Fig. 2.

Referring now in detail to the drawing, a stock screw Ill forces ahighly accelerated compound I2 including rubber, or a rubber-likematerial, as its essential ingredient along a bore I3 in an extrudingcylinder I4 through a strainer I6 positioned in a tapered opening i8 ina tool-holder 20 in an extruding head 22 concentric with a ,dit into the-taperedopening i8.

sage 4t inthe tool-holder 20.

2" tapered passage 24 in an adapter sleeve 25 aligned with vthe screw.

'Thetool-holder 20 is mounted removably in the head 22 by a nut -2'8 andbushings 3!) and l32. An aligning plate 34 holds a core-tube-holder 36and a die-holder -38 in alignment in a pas- The core-tubeholder 35 holdsa core tube 42 in alignment with a die 44 held by the die-holder 38.

The strainer I5 includes a fine mesh straining screen 46, a coarse meshbacking screen 48 andra spider-like backing plate Ell, `which nests inthe tapered openingl8. `The backing plate 50 includes a generallyannular, frustoconical centralpcrtion 52 andradial arms 6U-60, which Thecentral portion 52 has a passage B2 therethrough, and if desired couldhave a plurality of passages therethrough.

Operation The compound I2 is forced continuously along the extrudingcylinder I4 by the stock screw I0, and flows primarily along theportions of the tapered passage 24 near the periphery thereof withsubstantially lower velocity of ow in the central portion of the taperedpassage. The compound is free to pass through the strainer in the outerportions of the tapered passage, the slots formed between the radialarms Bilpermitting this flow, so that there is a minimum diversion ofthe major portion of the compound being forced through the extruding`head. Hence, dead spots, that is, spots of stagnant flow of thecompound, are minimized so that substantially all of the compound isiiushed rapidly through the extruding head. The compound is formed intoa covering around a conductive core. and is vulcanized in this form.

The radial, generally wedge-shaped slots formed between the arms 60--60of the backing plate 50 provide flow-passages of large crosssectionalareas so that the compound ows through the backing plate 50 with aminimum obstruction, and the arms provide excellent support for thebacking screen. Furthermore, the major portions of the areas of theseflow-passages are aligned with the outer portion of the passage 24 alongwhich inherently is the highest rate of flow of the compound.

' The strainer may be removed with ease from the tapered passage I8 inthe tool-holder 20, and the backing plate 53 is simple to clean, sincethe slots formed by the arms BCI-60 are wedge- Shaped and have open endsthrough which the 3 compound may be pulled. Since the strainer I6 islocated primarily in the tool-holder 20 (i. e., very close to the pointof extrusion of the cornn pound) and the compound is rapidly flushedthrough the tool-holder, heat imparted to the compound by the strainingthereof will not cause vulcanization prior to extrusion of the compound.The above-described apparatus also is excellent for extruding andstraining scorchy thermoplastic compounds, and will not scorch thethermoplastic compounds. The strength of the backing plate is notimpaired during the formation thereof as often occurs in the formationof past-known backing plates.

What is claimed is:

l. An apparatus for extruding and straining plastic compounds, whichcomprises an extrusion cylinder having a bore therein, a stock screwrotatably mounted in the bore for forcing plastic compound along theouter portions of the bore, Van extrusion head positioned at thedischarge end of the cylinder and having a tapered passage generallyaligned with and in communication with the bore, `a backing plate havinga tapered, tubular central portion and also provided with a plurality ofarms having flat supporting-edges extending generally radially outwardlyfrom the central portion and formed so as to nest in the taperedpassage, a coarse backing screen supported by the backing plate in aposition between the backing plate and the cylinder, and a finestraining screen supported by the coarse backing screen in a positionbetween the backing screen and the cylinder.

2. An apparatus for extruding and straining plastic compounds, whichcomprises an extrusion cylinder having a bore therein, a, stock screwrotatably mounted in the, bore for forcing plastic compound along theouter portions of the bore, an extrusion head positioned at thedischarge end of the cylinder and having a, tapered passage generallyaligned with and in communication with the bore, said head having anextrusion passage in communication with the discharge end of andextending transversely with respect to the tapered passage therein, alongitudinally tapered backing plate removably seated in the taperedpassage near the discharge end thereof, the backing plate being providedwith a plurality of transversely wedge-shaped slots extending from theperiphery thereo generally toward the center thereof for permitting flowof compound therethrough and along the outer portions of the taperedpassage in the head, a coarse backing screen supported in the taperedpassage by the backing plate on the approach side thereof, and a finestraining screen supported by the coarse backing screen on the approachside thereof.

GEORGE E. GLISS.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,471,324 Henning May 24, 1949FOREIGN PATENTS Number Country Date 269,761 Great Britain July 3, 1926

